import asyncio
import re


async def set_led(device: str, state: str) -> dict:
    """Set the locate LED on a drive via ledctl.

    Args:
        device: Block device name (e.g. "sda"). Must be alphanumeric.
        state: "locate" to turn on the locate LED, "off" to turn it off.
    """
    if not re.fullmatch(r"[a-zA-Z0-9]+", device):
        raise ValueError(f"Invalid device name: {device}")
    if state not in ("locate", "off"):
        raise ValueError(f"Invalid state: {state}")

    proc = await asyncio.create_subprocess_exec(
        "ledctl",
        f"{state}=/dev/{device}",
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
    )
    stdout, stderr = await proc.communicate()

    if proc.returncode != 0:
        err = stderr.decode().strip() or stdout.decode().strip()
        raise RuntimeError(f"ledctl failed (rc={proc.returncode}): {err}")

    return {"device": device, "state": state}